Method for producing highly-branched glycidol-based polyols

ABSTRACT

This invention relates to a process for the preparation of highly-branched polyols by polymerisation of glycidol in the presence of a hydrogen-active starter compound with basic catalysis, wherein glycidol is added in dilute solution and the solvent used for the dilution is continuously distilled off. The polyols thus prepared are colourless, contain as the core unit solely the starter compound used and have polydispersities of less than 1.7.

[0001] This invention relates to a process for the preparation ofhighly-branched polyols by polymerisation of glycidol in the presence ofa hydrogen-active starter compound with basic catalysis.

[0002] Branched polyols based on glycidol are conventionally prepared byreacting glycidol with a hydroxyl-containing compound, for example,glycerol, in the presence of inorganic (JP-A 61-43627) or organic (JP-A58-198429) acids as catalysts. The polymers thus obtained generally havea low degree of polymerisation. The polymerisation of glycidol toproducts of higher molecular weight which have a narrow molar-massdistribution and complete incorporation of initiators cannot be achievedby cationic catalysis, because of the competing cyclisation reactions(Macromolecules, 27 (1994) 320; Macromol Chem. Phys. 196 (1995) 1963).Existing processes using basic catalysis (EP-A 116 978; J. Polym. Sci.,23(4) (1985) 915), likewise do not lead to colourless products free ofby-products and having a narrow molar-mass distribution and completeincorporation of initiators. A secondary reaction of significance hereis in particular the cyclisation as a result of the autopolymerisationof glycidol.

[0003] Accordingly, the object of the present invention was to find aprocess for the preparation of highly-branched polyols based on glycidolwhereby the problems described above are avoided.

[0004] Surprisingly, it has now been found that it is possible toprepare colourless, highly-branched polyols based on glycidol which arenarrowly distributed and have a defined structure, if a dilute solutioncontaining glycidol is added to a hydrogen-active starter compound, withbasic catalysis, the solvent used for the dilution being continuouslydistilled off. In this connection, “defined structure” means that eachmolecule possesses the initiator (hydrogen-active starter compound) asthe core unit and the degree of polymerisation can be controlled via themonomer/initiator ratio.

[0005] The invention provides a process for the preparation ofhighly-branched polyols based on glycidol which have a definedstructure, which is characterised in that a dilute solution containingglycidol is added to a hydrogen-active starter compound, in the presenceof a basic catalyst, the solvent used for the dilution of the monomerbeing continuously distilled off.

[0006] As a result of the preferential opening of the epoxide ring atthe unsubstituted end where basic catalysis is used, a secondaryalkoxide is first of all produced, which, however, in consequence of thebasic catalysis, is in rapid exchange with the primary alkoxide. Therapid proton exchange equilibrium ensures that all hydroxyl groupspresent in the system are active as regards polymerisation and thatthere is a resulting development of branching.

[0007] Compounds having molecular weights of from 18 to 4,000 andcontaining from 1 to 20 hydroxyl, thiol and/or amino groups are used ashydrogen-active starter compounds. Examples which may be given are:methanol, ethanol, butanol, phenol, ethylene glycol, diethylene glycol,triethylene glycol, polyethylene glycol, 1,2-propylene glycol,dipropylene glycol, polypropylene glycol, 1,4-butanediol, hexamethyleneglycol, bisphenol A, trimethylolpropane, glycerol, pentaethritol,sorbitol, cane sugar, degraded starch, water, methylamine, ethylamine,propylamine, butylamine, stearylamine, aniline, benzylamine, o- andp-toluidine, a,β-naphthylalnine, ammonia, ethylenediarnine,propylenedianiine, 1,4-butylenediamone, 1,2-, 1,3-, 1,4, 1,5- or1,6-hexamethylenediamine, also o-, m- and p-phenylenediamine, 2,4-,2,6-tolylenediamine, 2,2′-:, 2,4- and 4,4′-diaminodiphenylmethane anddiethylenediamine, as well as compounds which contain functionalisablestarter groups, such as, for example, allyl glycerol, 10-undecenylamine,dibenzylamine, allyl alcohol, 10-undecenol. The starter compound isfirst of all partially deprotonated by a suitable reagent, for example,by alkali metals or alkaline-earth metals, their hydrides, alkoxides,hydroxides or alkyls. Preferably alkali metal hydroxides or alkoxides oralkaline-earth metal hydroxides or alkoxides are used, such as, forexample, potassium hydroxide or methoxide. Any reactive, volatilereaction products (for example, water, alcohol) which may form in thecourse of this are removed (for example, by distillation). Degrees ofdeprotonation are generally 0.1% to 90% and preferably 5% to 20%. Inorder to avoid problems of intermixture in the course of the reaction,the basic initiator system thus prepared is dissolved or dispersed,preferably under inert gas (for example, N₂, Ar), in an inert solvent I(0.1 to 90 wt. %, based on the quantity of the end product) having aboiling point at least 5° C. above the reaction temperature. Solvent Ican be an aliphatic, cycloaliphatic or aromatic hydrocarbon (forexample, Decalin, toluene, xylene) or an ether (for example, glyme,diglyme, triglyme), preferably diglyme, as well as mixtures of these.The monomer is added in a solution, which generally contains 80 to 0.1wt. % and preferably 50 to 1 wt. % glycidol in an inert solvent II.Solvent II can be an aliphatic, cycloaliphatic or aromatic hydrocarbon(for example, hexane, cyclohexane, benzene) or an ether (for example,diethyl ether, THF), preferably TBF, or a mixture of these, the boilingpoint being at least 1° C. below the reaction temperature. Solvent IIcan contain other additives, such as stabilisers and up to 10 wt. %,based on the solvent, of other comonomers such as, for example,propylene oxide, ethylene oxide, butylene oxide, vinyl oxirane, allyglycidyl ether, isopropyl glycidyl ether, phenyl glycidyl ether. SolventII must be a solvent for glycidol, but not necessarily for the polyol.The monomer solution is slowly added to the mixture of initiator andsolvent I, preferably under inert gas (for example, N₂, Ar). The feedrate is so chosen as to ensure a good temperature control at the givenreaction conditions of reaction temperature, glycidol concentration,hydroxyl and catalyst concentration. In the course of the reactionsolvent II is continuously removed from the reaction mixture bydistillation. Here the reaction temperatures are generally 40° C. to180° C., preferably 80° C. to 140° C. The reaction is preferably carriedout at normal pressure or reduced pressure. In the course of thereaction, depending on the choice of solvents I and II, the reactionmixture may become inhomogeneous. This does not influence the reaction,however, as long as no precipitation occurs. In order to work up thealkaline polymer, in principle all the known techniques for the workingup of polyether polyols for, applications in polyurethane chemistry maybe used (H. R., Friedel, in Gum, W. F., Riese, W. (Editors): “ReactionPolymers”, Hanser Verlag, Munich 1992, page 79). The polyol is worked uppreferably by neutralisation. For this, the alkaline polymer can firstof all be dissolved in a suitable solvent (for example, methanol). Theneutralisation is preferably carried out by acidification with dilutemineral acid (for example, sulfiric acid) with subsequent filtration ortreatment with adsorbent material (for example, magnesium silicate),particularly preferably by filtration through acidic ion-exchangematerial. This can be followed by a further purification byprecipitation (for example, from methanol in acetone). Finally, theproduct is freed from traces of solvents under vacuum at temperatures of20° C. to 200° C.

[0008] The polymerisation can be carried out in a system of reactorsconsisting of three essential components: a heatable reaction vesselwith mechanical stirrer, a metering unit and a system for the removal ofsolvents.

[0009] The polyols thus prepared, which are the subject matter of theApplication, have degrees of polymerisation (based on one activehydrogen atom of the initiator) of 1 to 300, preferably of 5 to 80. Themolar mass of the polyols according to the invention can be controlledvia the monomer/initiator ratio corresponding to the anionic process.The molar mass can be determined, for example, by vapour-pressureosmosis. The polydispersities are less than 1.7 and preferably less than1.5. They are determined by means of a GPC calibrated, for example, withpolypropylene glycol standards. The polyols contain as the core unit theinitiator used, which can be detected preferably by MALDI-TOF massspectrometry. The products are preferably colourless, but may also bepale yellowish in colour. The proportion of branched units in thehighly-branched polyols, based on all of the monomeric structural units,can be determined from the intensity of the signals in the ¹³C-NMRspectrum. The triply substituted carbon atom of the branched unitsexhibits a resonance between 79.5 ppm and 80.5 ppm (measured ind₄-methanol, inverse-gated technique). The proportion of the branchedunits is equal to three times the value of this integral value inrelation to the sum of the integrals of all signals of all units(branched, linear and terminal). The polyols prepared by the describedprocess have 10 to 33 mol %, preferably 20 to 33 mol %, branched units.In comparison with this, a perfect dendrimer has 50 mol % branched and50 mol % terminal units. A linear polymer, on the other hand, has nobranched units and only linear units and, depending on the initiator,one to two terminal units. With 20 to 33 mol % branched units, thepolyols described can therefore be termed highly-branched (see, forexample, Acta Polymer., 48 (1997) 30; Acta Polymer., 48 (1997) 298.

[0010] The highly-branched polyols thus prepared are versatile highlyfunctional polymeric intermediates. The great range of potentialinitiator molecules and the carefully calculated control of the degreeof polymerisation (and hence the degree of functionalisation) opens updiverse possible applications, thus for example, use as cross-linkingagents and additives in polyurethane formulations, in biocompatiblepolymers, in paints, adhesives and polymer blends, as support materialsfor catalysts and as active ingredients in medicine, biochemistry andsynthesis.

[0011] In addition, derivatisations can be carried out through carefullycalculated reactions of the functional groups.

[0012] By means of known per se reactions, the hydroxyl groups can, forexample, be esterified, etherified, aminated, alkylated, urethanised,halogenated, sulfonated, sulfated and oxidised. The terminal 1,2-diolgroups can, for example, be acetalated or ketalated or subjected to adiol cleavage.

[0013] Double bonds, which are introduced into the polyol, for example,via the starter compound, can likewise be derivatised in suitable form,for example, by hydroformulation or by radical or electrophilicaddition.

[0014] The polyols derivatised in this way in turn open up a multitudeof possible applications, thus, for example, use as cross-linking agentsand additives in polyurethane formulations, in biocompatible polymers,in paints, adhesives and polymer blends, as support materials forcatalysts and as active ingredients in medicine, biochemistry andsynthesis, as reaction compartments for the catalysis and production ofnanoparticles.

[0015] The highly-branched polyols prepared according to the inventioncan also be reacted with a second epoxide monomer (and optionallyfurther epoxide monomers) such as, for example, propylene oxide,ethylene oxide, butylene oxide, vinyl oxirane, glycidol, ally glycidylether, to form block copolymers. Preferably ethylene oxide, propyleneoxide, butylene oxide, vinyl oxirane and mixtures thereof are used.Preferably the highly-branched polyol is reacted, using basic catalysis,without intermediate working up and in the same reaction vessel, withthe epoxide monomer/mixture of epoxide monomers, optionally with theaddition of a solvent. A further deprotonation of the highly-branchedpolyol by means of the basic reagents described above may also takeplace. Degrees of deprotonation are generally 0.1%to 90% and preferably5% to 20%, based on one OH group. The reaction temperatures here arebetween 40° C. and 200° C., preferably between 20° C. and 180° C.,particularly preferably between 60° C. and 160° C. The reaction can becarried out at total pressures of between 0.001 and 20 bar. The blockcopolymers are worked up preferably by means of the techniques alreadydescribed above for worming up polyether polyols.

[0016] The block copolymers thus produced have degrees of polymerisation(based on one OH group of the highly-branched polyol used) of 1 to 70,preferably 1 to 10. The molar mass can be controlled via themonomer/initiator ratio corresponding to the anionic process. The molarmass can be determined, for example, by vapour-pressure osmosis. Thepolydispersities are less than 2.0 and preferably less than 1.5. Theyare determined by means of a GPC calibrated, for example, withpolypropylene glycol standards. The products are mainly colourless oils,which may also have a pale yellow colouring. The polymers have OH values(mg KOH equivalents per g polymer) between 750 and 14, preferablybetween 400 and 30.

[0017] The highly-branched block copolymers thus produced are versatilehighly functional polymeric intermediates. The great range ofblock-copolymer compositions opens up diverse possible applications,thus for example, use as cross-linking agents and additives inpolyurethane formulations, in biocompatible polymers, in paints,adhesives and polymer blends, as support materials for catalysts and asactive ingredients in medicine, biochemistry and synthesis, as reactioncompartments for the catalysis and production of nanoparticles, areaction compartment in this connection meaning a spatially limitedreaction space in the nanometric range.

EXAMPLES Example 1 Trimethylolpropane as Initiator

[0018] 1.2 g trimethylolpropane was melted in a 250 ml glass reactorheated to 100° C. and reacted with 0.7 ml potassium methoxide solution(25% in methanol) and excess methanol was then removed under vacuum, Theresidue was dissolved in 15 ml dry diglyme under an inert gas (Ar).Then, at 140° C., a solution of 34 g freshly distilled glycidol in 100ml dry TBF was added at a rate of 5 ml per hour to the reaction mixture,THF being continuously distilled off. On conclusion of the addition, thereaction mixture was dissolved in 150 ml methanol and neutralised byfiltration through an acidic ion-exchange resin (Amberlite® IR-120). Thefiltrate was precipitated out in 1600 ml acetone and the polymerobtained was dried for 12 hours at 80° C. under vacuum. 33 g of acolourless, highly viscous liquid having a molar mass of 3,700 (degreeof polymerisation 16 per active hydrogen) and a polydispersity of 1.15was obtained. All molecules contained the initiator as the core unit andhad 26% branched structural units.

Example 2 Polyethylene Glycol 600 as Initiator

[0019] As in the procedure described in Example 1, 6.0 g polyethyleneglycol having a molar mass of 600 was reacted with 0.25 ml potassiummonoxide solution (25% in methanol) at 100° C., excess methanol wasremoved under vacuum and the residue was dissolved in 10 ml dry diglyme.At a bath temperature of 140° C., 14 g glycidol in 100 ml dry THF wasadded at a rate of 5 ml per hour. The polymer was isolated as inExample 1. 19 g of a colourless, highly viscous liquid having a molarmass of 2,000 (degree of polymerisation 9.5 per active hydrogen) and apolydispersity of 1.13 was obtained. All molecules contained theinitiator as the core unit and had 26% branched structural units.

Example 3 Stearylamine as Initiator

[0020] 2.1 g stearylamine was melted in a 250 ml glass reactor heated to100° C. and reacted with 1.2 g glycidol. Then 0.9 ml potassium methoxidesolution (25% in methanol) was added and excess methanol was removedunder vacuum. The residue was dissolved in 15 ml dry diglyme at 140° C.55 g glycidol in 100 ml dry THF was added at a rate of 5 ml per hour.The polymer was isolated by a procedure similar to that in Example 1. 54g of a colourless, highly viscous liquid having a molar mass of 7,200(degree of polymerisation 47 per active hydrogen of the amine) and apolydispersity of 1.23 was obtained. All molecules contained theinitiator as the core unit and had 27% branched structural units.

Comparison Example 4 Procedure Without Solvents, Similar to EP-A 116 978

[0021] Under the conditions and with the educts from Example 2, thepolymerisation was carried out in the absence of any solvents andglycidol was added dropwise to the reaction mixture. 19 g of ayellowish, highly viscous liquid having a molar mass of 1,600 (degree ofpolymerisation 7 per active hydrogen) and a polydispersity of 1.84 wasobtained. Only 50% of all molecules contained the initiator as the coreunit.

Example 5 Production of Block Copolymer

[0022] In a 250 ml glass reactor heated to 100° C., 1.0 g of ahighly-branched polyol based on glycidol, prepared by the processdescribed in Example 1 and having a molar mass of 4,000 (correspondingto 52 OH terminal groups), was reacted with 0.1 equivalents of potassiumhydride per active hydrogen atom, 50 ml propylene oxide was added insuch a way that the internal temperature was maintained between 80° C.and 95° C. On conclusion of the addition, the reaction mixture wasdissolved in 150 ml methanol and neutralised by filtration through anacidic ion-exchange resin (Amberlite® IR-120). The filtrate was freedfrom methanol and dried for 12 hours at 80° C. under vacuum. 42 g of acolourless, highly viscous liquid having a molar mass of 12,300, apolydispersity of 1.3 and an OH value of 234 mg KOH/g was obtained.

1. Polyols based on glycidol and having a degree of polymerisation of 1to 300, a polydispersity of less than 1.7 and a content of branchedunits, based on the total monomeric structural units and determined by¹³C-NMR spectroscopy, of 10 to 33 mol %.
 2. Process for the preparationof polyols according to claim 1, wherein a dilute solution containingglycidol is added to a hydrogen-active starter compound, in the presenceof a basic catalyst and the solvent used for the dilution of the monomeris continuously distilled off.
 3. Polyols, obtainable by reacting thepolyols of claim 1 or obtained according to claim 2 with epoxidemonomers.
 4. Polyols, obtainable by reacting the polyols of claim 1 orobtained according to claim 2 with ethylene oxide, propylene oxide,butylene oxide, vinyl oxirane, ally glycidyl ether, isopropyl glycidylether, phenyl glycidyl ether or mixtures thereof.
 5. Use of the polyolsaccording to one or more of the claims 1, 3 and 4 or prepared by thepros of claim 2, and of derivatives prepared from them, as cross-linkingagents and additives in polyurethane formulations, in biocompatiblepolymers, in paints, adhesives and polymer blends, in support materialsfor catalysts and active ingredients, in reaction compartments for thecatalysis and production of nanoparticles.